1. Field of the Invention
The present invention relates to a carbon black and a process for producing the same. More particularly, the present invention relates to a coloring carbon black having both high blackness and excellent dispersibility, and to a process for producing the same.
2. Discussion of the Background
When a carbon black is used as pigment for resin, paint, or other use, dispersibility to the vehicle when kneaded to the resin, paint, or other vehicle as well as blackness and hue are of concern.
That is, in general carbon black used as a black pigment blended into paint or as another pigment, is required to have both high blackness and be easily dispersed when kneaded with the resin or vehicle and exhibit inherent blackness.
For this reason, for the purpose of getting carbon black used as resin coloring or paint that has both blackness and dispersibility, is was conventional to control properties such as specific surface area, DBP oil absorption, etc. For example, Japanese Examined Publication (KOKOKU) No. Showa 52-27632 (1977) reports, a carbon black having a specific surface area of about 120 m.sup.2 /g.about.430 m.sup.2 /g as suitable as a pigment for rubber, plastic paint, reinforcing agent, or other uses. But controlling only specific surface area is not enough for getting carbon black easily dispersible to resin, paint or other vehicles and exhibit blackness. Japanese Examined Publication (KOKOKU) No. Showa 52-41234 (1977) discloses carbon black with an Iodine adsorption of 200 mg/g and oil absorption of about 180.about.328% as a carbon black with high blackness and good dispersibility, but it doesn't show any other factor than specific surface area and oil absorption, that affects the dispersibility.
The references described above pay attention only to the blackness in the use as a pigment filler, etc., but no quality designing considering to the dispersibility to the resin or other vehicles is achieved. An object of the present invention is to obtain a carbon black having dispersibility showing high blackness, and to obtain a method for obtaining the same.
The present inventors have studied the effect of the basic structure of carbon black on the dispersibility in the vehicle, and they have found that, in addition to the conventionally used factors such as specific surface area, and dibutyl phthalate (DBP) oil absorption, by controlling the agglomerating degree and surface roughness within a certain range, one can get a carbon black having both high blackness and excellent dispersibility.